Spun bonded nonwoven fabrics have been used as surface material for absorptive products such as disposable diapers, because they are hardly napped or fluffed and have excellent fiber detachment resistance. However, continuous fibers (filaments or long fibers) that form the spun bonded nonwoven fabrics are difficult to make finer. Thus, the spun bonded nonwoven fabrics are difficult to provide a soft texture like that of meltblown nonwoven fabrics composed of extra-fine fibers. In addition, the spun bonded nonwoven fabrics have another drawback in that when their constituent fibers are made finer, more single fibers are cut short and thus more fibers of a larger fineness are mixed, leading to deterioration in texture.
Laid-open Japanese Patent Publication No. Sho 54-134177 discloses a meltblown nonwoven fabric composed of extra-fine polypropylene fibers, and Laid-open Japanese Patent Publication Nos. Sho 62-299501 and Hei 3-75056 disclose a disposable diaper employing a meltblown nonwoven fabric as its surface material. Meltblown nonwoven fabrics are advantageous in that they provide a soft texture due to their small fiber diameter. However, meltblown nonwoven fabrics have inherent drawbacks, including weak nonwoven fabric strength, generation of naps or fluffs, and tendency of permitting fiber detachment. In addition, they have such drawbacks that polymer particles are likely to be formed at the time of spinning, thus imparting the fabrics rough hand feeling, and the fabrics irritate the skin, making it unsuitable for disposable diapers for newborn babies. In order to improve the strength of meltblown nonwoven fabrics and to prevent fiber detachment, the meltblown nonwoven fabrics are being subjected to pressing with heated calender rolls or heated emboss rolls. However, the heat pressing must be performed under severe temperature and pressure conditions, leading to increase in the apparent density of the nonwoven fabrics and deterioration in the texture thereof.
Japanese Patent Publication No. Sho 60-11148 and Laid-open Japanese Patent Publication Nos. Hei 2-112458 and Hei 2-234967 disclose a laminated nonwoven fabric wherein a spun bonded nonwoven fabric is laminated on a meltblown nonwoven fabric, and the two layers are thermally fused to each other by the use of heated calender rolls, heated emboss rolls, or the likes. The resultant nonwoven fabric has improved strength as compared with that of conventional single-layer nonwoven fabrics. However, the nonwoven fabric has drawbacks, including unsatisfactory fusion between layers, poor fiber detachment resistance, and insufficient delamination strength, since regular fibers are used as continuous fibers that compose the spun bonded nonwoven fabric. In addition, in order to press the spun bonded nonwoven fabrics with heated emboss rolls, severe heating and pressing conditions are required, leading to drawbacks such as high apparent density and deterioration in texture.